It is typically desirable in the field of animal husbandry to selectively breed livestock. This breeding may be done by mating selected animals, artificially inseminating an animal, or any other suitable method. However, any breeding method used entails determining when the animal is in heat in order for insemination to fertilize the animal. The heat cycle is of a short duration and insemination must occur during the cycle. The accurate detection of estrus is a long recognized problem. If a pregnant cow is inseminated she is very apt to abort her calf. This problem makes false positives very expensive. With a false negative, the hot cow's breeding is delayed 21 days. This problem costs the dairyman $3.00 per day or $60.00 on each false negative.
Typically, when an animal, for example, a cow, is not in heat, she will not allow herself to be mounted. Conversely, when a cow is in heat, the cow will show an increased tendency to stand and permit itself to be mounted by other animals for an appreciable time. When the mounted animal allows the mounting animal to remain for about five seconds, a “standing mount” has occurred and the cow is classified as in standing heat. This condition occurs in the early stages of estrus. The most frequent mountings occur by bulls, but mountings are also made by other cows. Accordingly, the repeated mounting of a cow by any other such animal is a good indication that the cow is in heat. Cows must be mounted at least three times before safe to breed.
The identification of cows in heat has traditionally been accomplished by observation, the cows seen to allow mounting by other cows being separated from the herd. While visual inspection and observation of a herd may be employed to identify and segregate females in heat, because the heat cycle is of short duration, such visual observation must be conducted multiple times during a day and accompanied by immediate segregation or marking of the animals to be inseminated. Visual observation of the herd, which is often widely dispersed, is typically inefficient. Further, if no indicating device is used, unless the herd is maintained under constant visual observation, the heat cycle may go undetected in many animals.
A variety of devices have been developed for indicating when an animal is in heat by detecting when the animal has been mounted. Automatic indicators have been used that are attached to the top rear section of the animal between the hip-bone and spine and are set off by other animals mounting the animal in heat. Typically, the indicators rely on the pressure exerted by the chest or brisket of the mounting animal. A common indicator of this type includes a passive apparatus including a reservoir of marker fluid which is compressed by the mounting pressure to discharge some or all fluid and thereby mark the mounted animal. Frequently, these devices suffer from incidental seepage of the marker fluid. This seepage can result in an undesirably short shelf-life of the product. Further, the prior devices involve complicated dye packet devices that are undesirably complex and expensive.
A need has thus arisen for a detector for determining when a cow is in heat, wherein the detector is automatic and accurate for indicating when a cow has been mounted for a time equal to or greater than a predetermined time. A need has further arisen for a pressure responsive estrus detector which can be reset whereby the detector can be reused multiple times.